Spin test rigs are machines for testing the strength of machine parts rotating at high speeds, including, for example, rotors of turbines, compressors, high-speed electric motors, clutches, etc. A test rig of this type is known from DE 11 25 206 B.
DE 102 06 950 A1 further describes a high-speed rotation testing apparatus having a spindle holding a test object at its lower end, a driving motor for applying torque to the spindle, and a frame for supporting a rotor shaft of the driving motor. The shaft is arranged in the vertical direction of the apparatus, with the spindle being driven directly by coupling the upper ends of the rotor shaft and the spindle. A damping mechanism to limit vibration is provided in the vicinity of the lower end of the spindle. In a further embodiment, the high-speed rotation testing apparatus has a second spindle connected to the first spindle via a coupling so that their central axes are aligned with each other and the spindles rotate jointly. Extending from the first spindle, the second spindle extends downward and is in engagement with a weight supporting shaft and the damping mechanism, with the weight supporting shaft being supported by the casing by means of thrust bearings. The test object is secured to the lower end of the second spindle by means of a holding device.
Testing such rotors is performed at a test speed significantly higher than the maximum operating speed of the rotors. To fulfill their test task, spin test rigs therefore require a drive mechanism for very high rotational speeds. Drive mechanisms are known which use a transmission gear unit for generation of the high rotational speeds.
When testing rotors at overspeed, the test object is often subject to intentional or unintentional bursting. However, before the test object undergoes complete disintegration on account of centrifugal action, mass elements in the rotating test object tend to become displaced, thereby causing very large imbalances and, in consequence, high vibration amplitudes of the drive shaft supporting the test object. There exists therefore the demand for allowing large vibration amplitudes. In view of this requirement, spin test rigs have been developed reflecting a configuration in which the test object is mounted on a comparatively thin and hence highly elastic, vertically arranged shaft referred to as the spin shaft, hi addition, the spin shaft may be guided through a special, yielding damper bearing. By virtue of the elasticity of the spin shaft and the yielding nature of the damper bearing, the spin rig is capable of withstanding large vibration amplitudes in the presence of high rotational speeds.
When a spin test rig is configured to make allowance for the dynamics of the test object and the spin shaft, this results in a certain handling complexity regarding assembly and preparation of the test object for the spin test. Awkward handling proves to be a disadvantage particularly when the test object needs to be equipped with sensing devices for measurements during the spin test, which occurs frequently. Such measurements may be taken, for example, of temperatures and tensile stresses of the test object. To improve handling, known drive mechanisms for spin test rigs allow the spin shaft to be removed and, upon connection with the test object, to be replaced in the drive mechanism. Implementation of this design is, however, not always possible. Particularly in cases where small drive mechanisms rotating at very high speeds are used, reasons of geometry and strength forbid the removal of the spin shaft.